The dinoflagellates are one of the major groups of marine phytoplankton. This group of algae are primitive and have a long fossil record and consequently are thought by some biologists to be transition forms between the bacteria and higher eukaryotic organisms with respect to nuclear DNA arrangement. The objective of this project will be to continue to characterize in cytological, physical-chemical and genetic terms the chromosomes of dinoflagellates. Specifically, renaturation kinetics on other organisms will be determined. We plan DNA-DNA hybridization experiments, hybridizing the unique and repeated sequences separately, to determine genetic relatedness among various species of dinoflagellates. DNA-RNA hybridization studies will be carried out with both repeated and unique DNA to determine which sequences are transcribed. DNA replication will be studied as to size and shape of the replicating molecules using visoelasticity and electron microscopy and as to where in the cell cycle DNA replicates. Studies on the mechanism of chromosome folding are planned. Genetics (tetrad analysis) of two species will be continued.